Connection type between a power source and a progressing cavity pump for submersible application

ABSTRACT

A torque shaft, and couplings for connecting a progressing cavity pump and a driving part. The torque shaft, which accommodates the differing rotational motion of driver shaft and pump rotor, includes a shaft body and shaft heads both ends of the shaft body. The shaft heads have a transverse cross section of a hexagonal shape. An assembly for connecting a pump with a driving part which includes the above-mentioned torque shaft, a driver coupling, and a pump coupling and static components that connect the driving part housing to the progressing cavity pump stator. The connecting assembly includes provision for containing up thrust when the pump rotor rotation is reversed.

BACKGROUND OF THE INVENTION 1. Technical Field

The present invention relates to submersible apparatuses, and inparticular a shaft and shaft assembly connecting a progressing cavitypump and a driving part.

2. Background Art

A progressing cavity pump is a volumetric rotor pump that absorbs anddischarges liquid through the volumetric change of a series of sealedchambers. The simplest design of the progressing cavity pump consists ofa single external helix that revolves eccentrically within an internaldouble helix. The internal helix has the same minor diameter and twicethe pitch length of the external helix. The eccentricity is the locus ofthe rotor axis as its geometry rotates against the geometry of thestator. For oil field applications, the rotor is metal and the stator anelastomer that is injection molded within tubing. The rotor and statorare assembled with a compression fit. When the stator and rotor areassembled a series of cavities are formed. The cavities are sealed bythe fit comprised of two lines on the rotor 180° apart. As the rotorturns the cavities spiral (progress) along the pump axis so that as onecavity diminishes, the following cavity increases. The fluid crosssection is unchanged throughout the length of the stator, regardless ofrotor position, resulting in a pulsation-free, positive axial flow.

A progressing cavity pump can also consist of a multiple helix rotor andcorresponding stator—a multi-lobe pump. These are the preferred elementsfor drilling mud motors. Multiple helix designs can have any number ofhelices as long as there is one more helix in the stator than on itsmating rotor. For pumps, the most affordable and practical multi-lobepump design is a double helix rotor with a triple helix stator.

There is no inherent directionality in the progressing cavity pumpelements. There is no top or bottom until other equipment is attached.Though the helices of a pump are conventionally right hand, there isnothing between pump elements that dictate the direction of rotation. Ifa stator is constrained horizontally on a bench, the pump maybeassembled by inserting the rotor in one end then rotating it clockwiseinto the stator. The rotor is backed out with counterclockwise rotation.In operation, both rotor and stator are held against axial movement. Ifthe rotor is rotated clockwise, the fluid moves toward the viewer andthe thrust away. If counterclockwise, the fluid moves away from theviewer and the thrust opposite. Some of the power driving a progressingcavity pump is converted to thrust since the liquid moves along the sameaxis as the rotating parts.

A shaft connection between a motor, which shaft revolves concentrically,and an above described progressing cavity pump must, necessarily,accommodate eccentric revolution on one end to match the motion of thepump rotor. Such connection is most reliably accomplished with a torqueshaft.

The shaft connections for progressing cavity pumps that are currentlyavailable in the market have the following disadvantages:

Splines of conventional design, which are commonly employed at both endsof the shaft of the pump in the prior art, are easily susceptible tostress fatigue in spline connection when the pump operates continuously,resulting in problems such as a damage or fracturing of the spline.

Conventional splines require expensive machining processes for bothshaft and mating parts.

Damaged conventional splines are difficult to repair, especially in thefield.

Often, in conventional spline shafts, the spline is cut directly on abar of one continuous diameter so that the outside diameter of thespline is the same as the diameter of the body of the shaft. Thus, thetransverse cross section of the shaft is reduced at the spline,decreasing the maximum possible torque transmission.

In practical use, the pump rotation needs to be reversed for somereason. For example, the pump may be reversed for cleanup when the sandis produced in the oil wells. The pump rotor will move upwards whenoperated in reverse rotation. Thus, in the prior art, a thrust plate isadditionally placed on the top of the pump for preventing the pump rotorfrom being detached from the connector. The thrust plate is usuallyfixed by welding, and it requires a precise shop measurement tocorrectly position the thrust plate. This practice to some extentincreases the workload.

There remains a need for a shaft design that can address the technicalproblems in the prior art, such as a short service life due to stressfatigue readily caused by the torque shaft.

SUMMARY OF THE INVENTION

The present invention provides for a torque shaft, including a shaftbody, wherein the torque shaft includes shaft heads and a shaft body,the shaft heads are provided on both ends of the shaft body,respectively, and the shaft heads are configured to fix the shaft bodyto a driving and driven member, and each of the shaft heads has atransverse cross section of a hexagonal shape.

The present invention also provides for a connector for connecting aprogressing cavity pump and a driving part, wherein the connectorincludes the torque shaft above, and further includes a driver couplingand a pump coupling, wherein the couplings are provided with a hexagonalcavity compatible with the shaft heads, the driver coupling is installedon and fixed to one shaft head, and the pump coupling is installed onand fixed to the other shaft head, one end of the driving coupling has amating feature appropriate for attachment to the driving part shaft, oneend of the pump coupling has a mating feature appropriate for attachmentto the pump rotor, and each of the couplings is fixed to the shaft headby two fasteners passing through its outside diameter into either sideof the shaft head aperture, fixing the coupling to the shaft head fromaxial motion.

DESCRIPTION OF THE DRAWINGS

Other advantages of the present invention are readily appreciated as thesame becomes better understood by reference to the following detaileddescription when considered in connection with the accompanying drawingswherein:

FIG. 1 is a schematic diagram of the torque shaft provided according tothe First Embodiment;

FIG. 2 is a side view of the torque shaft provided according to theFirst Embodiment;

FIG. 3 is a schematic diagram of a connector for connecting a pump and adriving part, as provided according to the Second Embodiment; and

FIG. 4 is a partial enlarged view of the connector for connecting thepump and the driving part, and of the driving part connection end, asprovided according to the Second Embodiment.

The present invention generally provides for a torque shaft, as well ascouplings for connecting a progressing cavity pump and a driving part.

The torque shaft includes shaft heads 20 and a shaft body 10, where theshaft heads 20 are provided on both ends of the shaft body 10 and theshaft heads 20 are configured to fix the shaft body 10 to a driving anddriven member.

The shaft heads 20 have a transverse cross section of hexagonal shape.

Further, a transition part is provided between the shaft head 20 and theshaft body 10.

A second object of the present invention is to provide a connector forconnecting a progressing cavity pump and a driving part, so as toaddress the technical problems in the prior art.

The connector is composed of internal, rotating components, such as atorque shaft 100, and external, stationary components, such as a casing170.

Provided is a connector for connecting a pump and a driving part, wherethe connector includes the above-mentioned torque shaft 100 and furtherincludes a driver coupling 110 and a pump coupling 120. The torque shaftheads are inserted into corresponding hexagonal cavities in the drivercoupling 110 and the pump coupling 120.

Further, a fastener is also included for each coupling. The fastenerpasses through the outside diameter of each coupling into an aperture ineach shaft head, so as to fix the shaft heads to the couplings.

The driver coupling 110 possesses a suitable mating feature for thedriving part on one end. The pump coupling 120 possesses a suitablemating feature for the pump rotor on one end. A thrust nut 140 isattached to the driver coupling 110.

Further, a connector base 150, a thrust nipple 190, a connector casing170, and a pump stator adaption 160 are included.

The base 150 is fixedly connected to the driver part housing, the thrustnipple 190 is fixedly connected to the connector base 150, the connectorcasing 170 is fixedly connected to the thrust nipple 190, the pumpstator adaption 160 is fixedly connected to the connector casing 170,and the pump stator is fixedly connected to the pump stator adaption160.

The connector base 150 has an internal diameter nominally the same sizeas a corresponding diameter of the driver coupling 110. The diameterserves as a bearing surface for the coupling 110 so that the drivercoupling 110 rotates concentrically with the driver part shaft.

The thrust nipple 190 has an internal surface perpendicular to the axisof the driver coupling 110. This surface serves as an up thrust bearingwhen the coupling 110 is moved upward by reverse rotation of the pumprotor, engaging the thrust nut 140 attached to the driver coupling 110.The thrust nut 140 does not contact the thrust surface of the thrustnipple 190 when the pump is operating normally, the pump rotor is thrustis directed away from the thrust surface.

The connector casing 170 is provided outside the shaft body 10. Thecasing 170 is perforated to allow entry of well fluid to the suction endof the progressing cavity pump.

The present invention has the following beneficial effects:

The present invention provides a torque shaft including a shaft body 10;the shaft body 10 includes a shaft head 20 and a shaft body 10; and ashaft head 20 is provided on both ends of the shaft body 10. The shafthead 20 has a transverse cross section of hexagonal shape, namely, theshaft head 20 is provided as a hexagonal shaft head. The outer sidewallof the shaft segment of the shaft head 20 has six corners, and a planarstructure with a certain width is provided between adjacent corners.This increases the contact area when the shaft head 20 is connected, andaddresses the defects in splined connection, as employed in thetraditional technology, which is susceptible to stress fatigue when thetorque is transmitted due to multiple-corner structure of the spline.Corners, both at diametral changes in cross section in the transverseplane, increase the concentration of torque stress leading to increasedprobability of damage or fracture at the spline. Further, the hexagonalcross section provides increased cross section area when compared to aconventional spline of similar size, leading to increased torquecapacity.

The present invention also provides a connector for connecting a pumpand a driving part, which includes the above-mentioned torque shaft 100,a driver coupling 110, with thrust nut 140, and a pump coupling 120 andfurther includes a connector base 150, thrust nipple 190, connectorcasing 170, and pump stator adaption 160. Prior art includes a thrustplate welded on top of the progressing cavity pump stator, whichlocation is carefully established by shop measurements. The thrust plateis made necessary since a progressing cavity pump rotor will move upwardwhen the rotation is reversed, thus disengaging elements of the shaftingstring between the driving part and the pump. In the present invention,welding and measurement to establish location are eliminated. Further,the thrust surface provided in this disclosure is larger than ispossible at the top of a pump stator, and thus is more reliable.

The technical solutions of the present invention will be describedclearly and comprehensively by referring to the figures below. It isapparent that the embodiments to be described are part, but not all, ofthe embodiments of the present disclosure. All of the other embodimentsobtained by those skilled in the art from the embodiments of the presentinvention without making an inventive effort will fall within the scopeof the present invention as claimed.

It should be noted that, in the description of the present invention,unless otherwise expressly specified or defined, terms of “mount”,“couple”, and “connect” should be understood in broad sense. Forexample, a connection could be a fixed connection, a detachableconnection, or an integrated connection; it could be a mechanicalconnection or an electric connection; or it could be a directconnection, or an indirect connection via an intermediate medium, or itcould be an internal communication between two elements. The specificmeanings of the above-mentioned terms in the present invention could beunderstood by those skilled in the art according to specific situations.

Transverse is to be understood as perpendicular to the nominal axis ofthe shaft.

FIRST EMBODIMENT

As shown in FIGS. 1-2, the torque shaft provided in this embodimentincludes a shaft body 10; a shaft head 20 is provided on both ends ofthe shaft body 10. The shaft head 20 is configured to fix the shaft bodyto a driving member. The transverse cross section of the shaft head 20has a hexagonal shape.

Specifically, the torque shaft is comprised of a shaft body 10transitioning on both ends to a shaft head 20. The shaft head 20 is ashaft segment configured for fitting with a rotational component.Therefore, through the shaft head 20, the shaft body can be fixedlyconnected to the driving and driven member, for transmitting rotationalmotion and torque. The shaft body 10 is a non-fitting shaft segmentconnected to the shaft head 20.

Here, the shaft head 20 has a transverse cross section of hexagonalstructure. Namely, the shaft head 20 is provided as a hexagonal shafthead 20. The outer sidewall of its shaft segment has six corners, andthere is a planar structure with a certain width between the adjacentcorners. This increases the contact area when the shaft head 20 isconnected, and also distributes evenly the stress generated fromconnection. By fixing the shaft body 10 having a hexagonal shaft head 20to the rest of the driving members, it addresses the problems associatedwith splined connection in the traditional technology, that is, due tomultiple small radii inherent in splines of any type, which are stressconcentrators, the spline is susceptible to stress fatigue when thetorque is transmitted, which leads to a damage or fracture of thespline.

In the optional aspects of this embodiment, as shown in FIGS. 1-2, theshaft head 20 is provided thereon with a fixing aperture 30. The fixingaperture 30 passes through the shaft head 20 perpendicular to the axisof the shaft head 20.

Specifically, the fixing aperture 30 is provided on the shaft head 20close to the end face, and the fixing aperture 30 is configured to passthrough the shaft head 20 perpendicular to the axis of the shaft head20. The torque shaft can be fixedly connected to other components by aconnecting member such as a screw passing through or into the fixingaperture 30.

Here, a fixed connection is achieved by a locking screw passing throughthe fixing aperture 30.

Specifically, one end of the torque shaft is coupled to the progressingcavity pump rotor and the other end is coupled to the driving part, sothe torque shaft is mainly configured to transmit motion and torque. Thetorque shaft includes a shaft body 10 and shaft heads 20 at both ends.The shaft head 20 is configured to connect to the pump rotor and to thedriving part, and the shaft body 10 acts as a joining part; when theshaft head 20 is coupled to the pump rotor and to the driving part, inorder to prevent the connection from separating, the shaft head 20 needsto be fixed to the coupling thereto. Thus, a screw or other fastener isinserted through the coupling into the aperture 30.

In the optional aspect of this embodiment, as shown in FIGS. 1-2, atransition area is provided between the shaft heads 20 and the shaftbody 10.

In an optional aspect of this embodiment, as shown in FIGS. 1-2, thetransition part includes a circular arc transition area 40 and acylindrical transition area 50.

Specifically, the transition part is provided between the shaft body 10and the shaft head 20. The transition part includes a cylindricaltransition area 50 and a circular arc transition area 40. The circulararc transition area 40 is provided at a position where the shaft body 10is between part and the cylindrical transition area 50 is providedbetween the circular arc transition area 40 and shaft head 20.

Here, the circular arc transition area 40 is configured to reduce thestress concentration at the shaft body 10 of the torque shaft due to anabrupt change in the cross section between the shaft body 10 and thehead 20 which will otherwise reduce the service life of the torqueshaft. The cylindrical transition area 50 is configured to provide astandoff surface to protect the shaft head 10 during handling andstorage.

Here, the torque shaft, consisting of the main body 50, the circular arctransition area 40, the cylindrical transition area 40, and the shafthead 10, is made from a single blank sucker rod forging.

Specifically, since sucker rods are used to drive progressing cavitypumps in some applications, transmit similar torque, transmit similarmotion, are exposed to well fluid, and have similar geometry, the suckerrod forging is an especially suitable selection for torque shaftmaterial. Such a forging is made so that the main body 10 is alreadyformed and it transitions through an already formed circular arc 40 toupset ends with a diameter larger than the main body 10 and larger thanthe cylindrical transition area and shaft head. The upset ends aremachined to form the cylindrical transition area and shaft head.

Here, the forged transition to a larger diameter is an improvement overcurrent practice of turning bar down to the diameter of the main body inthat the forging forms the grain of the material to follow the contourof the ultimate torque shaft surface in contrast to cutting across thematerial grain when making shaft in current practice. The continuousgrains provide a more fatigue resistant torque shaft.

SECOND EMBODIMENT

The present invention also provides a connector for connecting aprogressing cavity pump and a driving part. As shown in FIGS. 3-4, theconnector for connecting the progressing cavity pump and the drivingpart as provided according to this embodiment has rotating componentswhich include the above-mentioned torque shaft 100, and also include adriver coupling 110, a thrust nut 140, and a pump coupling 120. Further,this embodiment has static components which include a connector base150, a thrust nipple 190, a connector casing, and a pump stator adaption160.

Here, the one end of the driving coupling 110 is configured to connect adriving part, for example, to connect a protector in the driving part,and one end of the driven coupling 120 is configured to connect aprogressing cavity pump.

Specifically, the driver and driving couplings each have a hexagonalcavity on one end corresponding to the transverse hexagonal crosssection of the shaft head 20. The driver coupling 110 is internallysplined on one end corresponding to the conventionally provided externalspline of the driving part. The driven coupling 120 is internallythreaded on one end corresponding to the conventionally provided suckerrod thread on the pump rotor. The driven coupling is installed onto thepump rotor, applying the torque appropriate for the pump rotor threadsize, thus fixing the driven coupling to the pump rotor. One torqueshaft head 20 is inserted into the driving coupling 110 cavity and fixedby inserting locking screws 130 through the coupling into the aperture30, similarly, the other torque shaft head 20 is inserted into thedriven coupling 120 cavity and fixed using locking screws 130. Thus, thedriving coupling 110, torque shaft 100, the driven coupling, and thepump rotor are fixed torsionally and axially so will move as oneassembly.

A thrust nut 140 is installed onto the driving coupling 110, and itrotates and travels axially as one with the driving coupling 110.

Specifically, the nut 140 is threaded onto the outside diameter of thedriven coupling 110 and located firmly at one end against a shoulder.The nut 140 able to bear an axial force imposed in an upward direction.During normal operation of the progressing cavity pump, the thrust nut140 is spaced so that there is no contact with any portion of the staticcomponents of the connector.

By fixedly connecting the pump rotor, the driving coupling 110, withthrust nut 140, the torque shaft 100, and the driven coupling 120, thethrust nut 140 will engage the thrust nipple 190 when the pump rotor isrevolving in reverse. Thus, the rotor will remain in place. Moreover, inthe prior art, in order to prevent the progressing cavity pump frommoving upwards when run in reverse, a thrust plate is welded on the topof the progressing cavity pump. Since the thrust plate is welded ontothe progressing cavity pump, it is not easy to replace the thrust plateafter being damaged. Furthermore, careful shop measurements arenecessary to correctly position the thrust plate. To some extent, theassembly time is increased. In the present embodiment, however, theextensive measurement and welding are avoided.

In an additional aspect of this embodiment, as shown in FIGS. 3-4, aspacer 180 is further included. The spacer 180 is provided on thedriving coupling 110 between the connector base 150 and the drivercoupling 110. The spacer 180 is configured to limit downward movement ofthe driving coupling 110 during handling. Once the connector isinstalled with the driving part, the spacer 180 serves no furtherpurpose.

In an optional aspect of this embodiment, as shown in FIGS. 3-4, thisembodiment has static components which include a connector base 150, athrust nipple 190, a connector casing, and a pump stator adaption 160.

Specifically, the connector base 150 attaches to the housing of thedriving part and threads into the thrust nipple 190. Additionally,internally, the connector base 150 has a cylindrical bearing surfacewhich is sized for the outside diameter of the lower part of the drivingcoupling 110. The driving coupling 110 revolves within and against theconnector base 150, thus the revolution of the driving coupling 110 isconcentric with the axis of the driving part assuring that one end ofthe torque shaft 100 is revolving concentrically and isolating thedriving part from the orbiting eccentricity of the pump rotor. Thethrust nipple 190 threads onto the base 150 and threads into theconnector casing 170. Additionally, internally, the thrust nipple 190has a transverse bearing surface which serves to engage the thrust nut140 should the pump rotor travel upward on reverse rotation of the pump.The connector casing 170 threads onto the thrust nipple 150 and threadsonto the pump stator adaption 160. Additionally, the connector casing isperforated with multiple small holes to allow the passage of well fluid,thus the connector casing 170 serves as the progressing cavity pumpintake. The pump stator adaption 160 threads into the connector casing170 and threads into the pump stator. The pump stator adaption 160adapts the connector casing to the various progressing cavity pumpstator thread sizes and types.

Finally, it should be noted that the above embodiments are merelyintended to explain the technical solutions of the application and arenot intended to limit the application. Although the present inventionhas been illustrated in detail with reference to the foregoingembodiments, it would be understood by persons of ordinary skill in theart that the technical solutions described in the foregoing embodimentscan still be modified, or that part or all of the technical featuresthereof can be replaced by equivalent substitution. These modificationsor substitutions do not cause the principle of the correspondingtechnical solutions to depart from the scope of the technical solutionsof the embodiments of the application.

Throughout this application, various publications, including UnitedStates patents, are referenced by author and year and patents by number.Full citations for the publications are listed below. The disclosures ofthese publications and patents in their entireties are herebyincorporated by reference into this application in order to more fullydescribe the state of the art to which this invention pertains.

The invention has been described in an illustrative manner, and it is tobe understood that the terminology, which has been used is intended tobe in the nature of words of description rather than of limitation.

Obviously, many modifications and variations of the present inventionare possible in light of the above teachings. It is, therefore, to beunderstood that within the scope of the appended claims, the inventioncan be practiced otherwise than as specifically described.

What is claimed is:
 1. A torque shaft, comprising a shaft body, whereinthe torque shaft comprises shaft heads and a shaft body, the shaft headsare provided on both ends of the shaft body, respectively, and the shaftheads are configured to fix the shaft body to a driving and drivenmember; and each of the shaft heads has a transverse cross section of ahexagonal shape.
 2. The torque shaft according to claim 1, wherein afixing aperture is provided on each of the shaft heads, and the fixingaperture runs through the shaft head perpendicular to the axis of theshaft head.
 3. The torque shaft according to claim 1, wherein atransition part is provided between each of the shaft heads and theshaft body.
 4. The torque shaft according to claim 3, wherein thetransition part comprises a circular arc transition area and acylindrical transition area, and the circular arc transition area isprovided at either end of the shaft body.
 5. A connector for connectinga progressing cavity pump and a driving part, wherein the connectorcomprises the torque shaft of claim 1, and further comprises a drivercoupling and a pump coupling, wherein the couplings are provided with ahexagonal cavity compatible with the shaft heads, the driver coupling isinstalled on and fixed to one shaft head, and the pump coupling isinstalled on and fixed to the other shaft head, one end of the drivingcoupling has a mating feature appropriate for attachment to the drivingpart shaft, one end of the pump coupling has a mating featureappropriate for attachment to the pump rotor, and each of the couplingsis fixed to the shaft head by two fasteners passing through its outsidediameter into either side of the shaft head aperture, fixing thecoupling to the shaft head from axial motion.
 6. The connector forconnecting a progressing cavity pump and a driving part according toclaim 5, wherein the connector further comprises a connecting base, athrust nipple, a connector casing, and a pump stator adaption, whereinthe driver part housing is fixedly connected to the connector base, thethrust nipple is fixedly connected to the connector base, the connectorcasing is fixedly connected to the thrust nipple, the pump statoradaption is fixedly connected to the connector casing, and theprogressing cavity pump stator is fixedly connected to the pump statoradaption, the connector casing is perforated to allow passage of wellfluid, the connector base has an internal cylindrical bearing surface,nominally sized as the lower outside diameter of the driver coupling,which serves to constrain the driver coupling rotation concentric tothat of the driver, and the thrust nipple has an internal surfaceperpendicular to its central axis at its upper end which serves as anupward thrust bearing surface.
 7. The connector for connecting aprogressing cavity pump and a driving part according to claim 6, whereinthe connector further comprises a thrust nut, the thrust nut is fixedlyattached to the driving coupling, and during normal operation of theprogressing cavity pump, the rotor thrust direction is away from thethrust surface of the thrust nipple so that the thrust nut is not incontact with the thrust nipple.
 8. The connector for connecting aprogressing cavity pump and a driving part according to claim 7, whereina spacer is provided on the driving coupling, located between thedriving coupling and the connecting base.